A Vendor Lock-In is when certain software is developed to be incompatible by design with other software that have similar functionality. It is used to establish a monopoly. And any such function is malicious.
This comment thread is for people to document various implementations of this malicious feature.
I made myself review both Avatar movies in one day, which was something I had to do to see the progress, or lack thereof of James Cameron. And there is progress. A lot of it!